This proposal outlines several approaches to the study of resistance plasmids in bacteria, their phenotypes, the control of their expression and their interrelationships. Work will concentrate on studies of the mechanisms of antibiotic resistance, especially the aminoglycosides. Mechanisms of resistance will be related to mechanisms of action and transport of these antibiotics. Plasmids of resistant strains of hospital outbreaks will be especially important because of the relationship to the infectious spread of resistance. Relationships between clinically important plasmids and resistance determinants will be studied by restriction endonuclease analysis, recombinant plasmid studies and hemology studies. The role of transposable elements in these events will also be investigated. In addition, as a separate project, we plan to continue with our analysis of the KsgA locus in E. coli, a gene that determines a specific ribosomal RNA methylase. Since the gene for the methylase has been cloned we can determine the sequence of the promoter for this gene and its relation to other ribosomal promoters.